Human aging is associated with glucose intolerance and changes in insulin sensitivity but age effects on pancreatic beta cell function in humans are not clear. Insulin sensitivity can be changed by several pharmacological agents one of which is troglitazone which enhances insulin sensitivity. We propose to study insulin secretion responses of young and elderly subjects (with and without impaired glucose tolerance) before and after troglitazone administration to observe the effect aging has on pancreatic beta cell adaptation to increased insulin sensitivity.